Although a large amount of research has been conducted into monoazo dyestuffs as colorants for polyesters, and a somewhat lesser degree of exploration has been conducted in the field of disazos, little attention has been focused on the area of trisazos as polyester colors, undoubtedly due to the prejudice against such large molecules as dyestuffs for polyesters. There have been reported in the literature various research efforts in the area of trisazos. Lewcock reports the preparation of a p,p'"-dihydroxytrisazo (J. Soc. Chem. Ind., P.44, 154T). Conrad, U.S. Pat. No. 2,090,938 explored various trisazos based upon naphthalene, which are principally reported as being colorants for oils, fats and waxes, particularly for nitrocellulose lacquers, resins, varnishes, wood stains, printing and stamping inks, artificial leathers, patent leather, shoe polishes and creams, soaps, gasolines and the like. Other related research efforts have been reported in the nineteenth century, including 1892 British complete specification no. 277 and German patents 80,421 and 84,289. In spite of the long history into the exploration of the structures of these compounds going back to the previous century, there has been no interest shown in these dyestuffs for polyester fabrics, undoubtedly because of the large size of these compounds.
It has now been discovered that p,p'"-dihydroxytrisazos produce excellent dyeings on polyester fabrics, particularly poly(ethylene terephthalate) and poly(1,4-cyclohexylenedimethylene)terephthalate.